Hi,

tie one end of three identical pieces of thread together. That shud loo like -

\******/
*\****/
**\**/
***\/
***|
***|
***|
( Spare me for my 'not so well' drawing ! The '*' are for proper indentation)

on a horizontal table attach 3 pulleys at the three vertices of the triangle whose fermat's pt. is to be located. pass the free ends of the 3 threads over the pulleys and attach equal weights at those ends.

When freely suspended, the system comes into equilibrium when the tied end of the 3 threads coincides with the fermat point.

I hope I am correct...What say?

d:-)
Deep G